Study: Small aircraft face risks near wind farms

1/17/2014

Special to The Hays Daily News

LAWRENCE -- A study from the University of Kansas School of Engineering points to potential safety hazards that could affect hundreds of airports throughout the country and calls for updated guidelines to improve aviation safety.

At issue is the proximity of wind farms to general aviation airports and how the small aircraft that use them could be affected by turbulence generated by wind turbines.

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Special to The Hays Daily News

LAWRENCE -- A study from the University of Kansas School of Engineering points to potential safety hazards that could affect hundreds of airports throughout the country and calls for updated guidelines to improve aviation safety.

At issue is the proximity of wind farms to general aviation airports and how the small aircraft that use them could be affected by turbulence generated by wind turbines.

"We're really looking at two potential threats," said Tom Mulinazzi, professor of civil, environmental and architectural engineering. "These turbines can set up a circular vortex that can roll a plane if it gets in there. And they can increase crosswind speeds above what's expected, which can be a real danger to small aircraft which don't typically take off and land with crosswinds stronger than about 12 mph."

Professor of aerospace engineering Charlie Zheng, graduate student Anpeng He and Mulinazzi co-authored the report for the aviation division of the Kansas Department of Transportation.

By using advance computer modeling, the research team studied the effect of winds from 10 mph to 40 mph. They found the higher the wind speed, the farther the turbulence reached -- stretching as much as 3 miles from a single turbine -- before dissipating.

Mulinazzi and Zheng used data from proposed wind farms near airports in both Rooks and Pratt counties.

At both airports, within nearly 3 miles of the runway, pilots potentially could encounter a crosswind generated from a turbine capable of rolling the aircraft.

KU initially said the Rooks County wind farm was operational, but the project never got off the drawing board.

Mulinazzi and Zheng recently presented their findings at the inaugural Kansas Aviation Expo in Wichita. Mulinazzi said it appears this study is the first of its kind in the United States. Federal Aviation Administration guidelines only evaluate objects that might physically protrude into the invisible boundaries that extend upward and outward from the center-line of a runway.

"The FAA reviews the potential hazard of the physical height and location of any structure, but not any of the emissions from that structure," said Tiffany Brown, state aviation engineer.

with KDOT's Aviation Division. "This research points out a shortcoming in the current evaluation process, and that is why this is so important."

KU is at the leading edge of studying this potential hazard.

"We found no research that looked at the impact of wind generated by wind farms on general aviation," Mulinazzi said. "But KDOT tells us they've been getting complaints from pilots about unexpected turbulence as they approach runways near wind farms. So we felt like the study was worthwhile, especially with the boom in wind farms and wind farm proposals in Kansas."

Kansas has approximately 140 public-use airports and many more private-use airports. There are 16 wind farms operating in Kansas today, but there are proposals for an additional 58, with some planned in close proximity to existing airports.

"So as state and local leaders consider these proposals for new wind farms, we're hoping to provide them with specific information they can use to create guidelines to ensure aircraft safety. Right now, there's really nothing on the books," Mulinazzi said.

Previous research into turbulence generated by wind farms had shown planes briefly could disappear on radar when flying near a turbine, because radar interprets the movement of the blades as precipitation, which can mask the radar return of an aircraft. No previous research had analyzed the actual effect of this turbulence on aircraft handling and performance, Mulinazzi said.